Photomultiplier and radiation detector

Abstract

A holding member or a base member, through which stem pins are passed and one surface of which is held by the holding member, is joined to the stem pins and the holding member by fusion by the melting of the base member. Upon melting, a volume of the base member is made to escape into a base member seep portion, and a stem is arranged as a two-layer arrangement formed by the holding of the base member by the holding member. When the holding member is joined to the inner surface of the base member, the inner surface of the stem is improved in positional precision, flatness, and levelness, while when the holding member is joined to the outer surface of the base member, the outer surface of the stem is improved in positional precision, flatness, and levelness.

1. A photomultiplier comprising:
 a photoelectric surface disposed inside a sealed container, which is put in a vacuum state, and converting incident light made incident through a light receiving plate into electrons, which forms an end portion at one side of the sealed container; 
 an electron multiplier unit disposed inside the sealed container and multiplying electrons emitted from the photoelectric surface; 
 an anode disposed inside the sealed container and used for taking out the electrons multiplied by the electron multiplier unit as an output signal; 
 a stem forming an end portion at the other side of the sealed container and having a base member, with an insulating property, and a holding member, having a melting point higher than that of the base member and being joined to one of an inner surface and an outer surface of the base member; and 
 a plurality of stem pins insertedly mounted in the stem and leading to the exterior from inside the sealed container and electrically connected to the anode and the electron multiplier unit, 
 wherein the stem pins are passed through and joined to the base member, and 
 the electron multiplier unit and the anode are layered on the inner surface of the stem, and 
 the base member and the holding member, and the base member and the stem pins are respectively joined by fusion by the melting of the base member, and 
 a base member seep portion, into which the base member seeps upon melting, is disposed in at least one of the holding member and the base member. 
 
   
   
     2. The photomultiplier according to  claim 1 , wherein the holding member has a plurality of openings, through which the stem pins joined to the base member are inserted, and among the openings, at least two are made larger in diameter than the other openings. 
   
   
     3. A radiation detector comprising:
 a photomultiplier including:
 a photoelectric surface disposed inside a sealed container, which is put in a vacuum state, and converting incident light made incident through a light receiving plate into electrons, which forms an end portion at one side of the sealed container; 
 an electron multiplier unit disposed inside the sealed container and multiplying electrons emitted from the photoelectric surface; 
 an anode disposed inside the sealed container and used for taking out the electrons multiplied by the electron multiplier unit as an output signal; 
 a stem forming an end portion at the other side of the sealed container and having a base member, with an insulating property, and a holding member, having a melting point higher than that of the base member and being joined to one of an inner surface and an outer surface of the base member; and 
 a plurality of stem pins insertedly mounted in the stem and leading to the exterior from inside the sealed container and electrically connected to the anode and the electron multiplier unit, wherein the stem pins are passed through and joined to the base member, and 
 the electron multiplier unit and the anode are layered on the inner surface of the stem, and 
 the base member and the holding member, and the base member and the stem pins are respectively joined by fusion by the melting of the base member; and 
 a base member seep portion, into which the base member seeps upon melting, is disposed in at least one of the holding member and the base member; and 
 
 a scintillator, convening radiation into light and emitting the light, installed at the outer side of the light receiving plate of the photomultiplier.